This invention is directed to a lamp assembly, and more particularly a lamp assembly for use in measuring pressure on a surface painted with pressure sensitive paint.
Accurate determination of aircraft component loads from wind tunnel testing is critical to the development of any air vehicle. Traditional techniques utilize many surface pressure taps distributed over the surface of a wind tunnel model to obtain an estimate of the surface pressure distribution. Physical and mechanical constraints of typical test articles limit the number of pressure taps that can be used to define the actual surface pressure distribution over the entire surface. Pressure taps provide a reading of the pressure at one point only on the surface, and must be connected to pressure transducers by using individual flexible tubing. A wind tunnel model can easily require a large number of such taps, such that the total installation cost for testing a particular model can become quite high. Moreover, while such taps provide readings of the pressures at the points where such taps are installed, it becomes a significant challenge when using taps alone to determine the air pressure between the tap locations, which is required in order to create a complete surface pressure map over the entire air vehicle which then can be used to determine the integrated loads on various aerodynamic surfaces.
The traditional method requires a significant amount of manual interaction and creative engineering judgment. Inherent inaccuracies exist in this approach since there is a high probability that localized flow features are missed by the taps alone. Wind tunnel testing is a pacing item in the length of the design cycle of an aircraft, and a shortened cycle results in significant cost savings.
Pressure sensitive paint (PSP) requires only a few surface pressure taps and uses an optical technique to obtain the pressure at every point over the model surface. Although the pressure transducers are more accurate than the PSP at a given point, that PSP provides a continuum of pressure over the model produces a significant advantage over the traditional approach. In addition, the process by which the pressures are transformed onto a finite element model of the aircraft is significantly shortened.
In making accurate PSP measurements to determine aircraft component loads, the requirements for the PSP illumination system have become even more critical. The illumination source must be (1) extremely stable in time while also withstanding changes in temperature and pressure, (2) provide the proper wavelengths of light with very little or no leakage in the detection band, and (3) be easy to install, adjust, and remove from the test facility. Equally important, the illumination source must be protected from overheating to avoid failure.